How to prevent frequent flooding

With the ice caps melting, more water is poured into the oceans, thus raising their levels. The seas invade low-lying areas. If the melting of the ice does not stop, low-lying islands will disappear; the bigger ones will shrink as the seas overwhelm their shores.

The second factor is logging, at least in the Philippines. Greedy loggers have ravaged our forests, and most of our mountains are now bald. Without trees, there are no roots to hold the soil together. Thus, rainwater easily erodes the mountainsides, carrying the topsoil down to streams and rivers below. As the water flows down the waterways, it drops the silt it is carrying. Over the years, this silt makes the waterways shallower, so they can hold less and less water. Thus they easily overflow their banks.

Floodwaters are now brown, unlike before when they were clearer and cleaner. That is because of the silt. When the floods recede, they leave a thick layer of mud. That is the mud they deposit at the bottom of waterways.

The reservoirs of the dams from which we get our water are also now much shallower and can hold less water because their watersheds are also denuded. That is why they reach spilling level faster and go dry faster in summer.

When waterways overflow their banks, the water can only flow into our streets, homes and fields. These are the floods that we have to endure more and more frequently.

The third factor is the rapid development of the countryside. With more housing on what were once rice fields, the construction of more office buildings, malls and condominiums in the cities, and the paving of more streets and parking lots, a layer of non-porous concrete covers larger areas of land. Rain and floodwaters cannot pierce this layer to seep through the ground and the underground aquifers as they used to do. 

The fourth factor is the inadequate drainage system. Planners did not anticipate the big volumes of water that would inundate the land. The drainage system cannot drain rain and floodwaters fast enough.

The fifth factor is garbage, specifically the bad habit of many Filipinos in throwing trash anywhere, especially into waterways. This trash clogs pipes and the canals that used to be very effective drainage and transportation systems. Look at any canal in Manila and you will see garbage floating on the surface. Look at any seaside village or coastal town and you will see garbage the waves have dumped on the shore. After every storm, Roxas Boulevard, once a beautiful promenade with a magnificent view of the Manila Bay sunset, is littered with garbage brought in by the waves.

Don’t blame the sea; blame humans. It is so easy to put one’s trash in a garbage can, but it is much easier for the lazy to just dump it out the window and into the canal, river, or sea, and forget about the consequences.

This floating garbage blocks floodwaters from flowing into the sea. The outlets of rivers to Manila Bay have been made shallow by garbage so that river water cannot empty into the bay fast enough. The water backs up, overflows riverbanks and floods surrounding areas.

The outlet of Laguna Lake to Manila Bay has also been made shallower by silt and garbage. Planners are considering widening this outlet. It should also be dredged and made deeper.

What can we do to improve the situation?

Reduce all forms of burning so that the emission of greenhouse gases is reduced, to stop or slow the rise in the earth’s temperature. That will help stop or slow down the melting of the ice caps and the rising levels of the oceans. Vehicles, power plants, factories burning coal, and planters burning huge tracts of the rainforests are the worst polluters of the earth’s atmosphere.

Leave more areas open to agriculture, parks, gardens and other open spaces, to leave rainwater more room to seep into the ground.

Stop all logging, legal and illegal.

Dredge waterways and lakes.

Unclog drainage pipes and keep them clear of garbage.

Improve the drainage system.

Easiest of all: use your common sense. Don’t throw garbage into waterways, or anywhere else except a trash can.